tail 



oes 



FIG. 453. Illustrating tlie metamorphosis of the tadpole of Ciona intestinalis. 

 (After Willey.) 



A, young tadpole just after fixation, seen from the right side the mouth is still in the larval position 

 and the tail is just beginning to degenerate. B, young fixed Ciona, in which the mouth is rotated up- 

 wards and the tail is reduced to a granular mass. C, young fixed Ciona, in which the mouth has attained 

 the upper pole of the animal and in which the tail has disappeared, a, anus ; at, atrial canal ; b.v, 

 brain-vesicle ; endst, endostyle ; gang.al, adult ganglion ; jr.si-*, the first four gill-slits ; hyp, hypophysial 

 canal ; int, intestine ; ra, mouth ; mn, chin (mental process) ; n.c, nerve cord ; n.t, nerve tube ; oes, 

 oesophagus ; pc, pericardial sac ; pph, peripharyngeal ciliated band ; py.g, pyloric gland ; st, stomach. 



% 623 



